As the demand from users for bandwidth is rapidly increasing, optical transmission systems, where subscriber traffic is transmitted using optical networks, is installed to serve this demand. These networks are typically referred to as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), fiber-to-the-premise (FTTP), or fiber-to-the-home (FTTH). Each such network provides an access from a central office (CO) to a building, or a home, via optical fibers installed near or up to the subscribers' locations. As the transmission quantity of such an optical cable is much greater than the bandwidth actually required by each subscriber, a passive optical network (PON), shared between a plurality of subscribers through a splitter, was developed.
An exemplary diagram of a typical PON 100 is schematically shown in FIG. 1. The PON 100 includes M optical network units (ONUs) 120-1, 120-2, through 120-M, coupled to an optical line terminal (OLT) 130 via a passive optical splitter 140. To the extent that reference is made to the ONUs without regard to a specific one thereof, such ONUs will be referenced as 120. Traffic data transmission may be achieved by using asynchronous transfer mode (ATM) cells over two optical wavelengths, one for the downstream direction and another for the upstream direction. Downstream transmission from OLT 130 is broadcast to all ONUs 120. Each ONU 120 filters its respective data according to, for example, pre-assigned ATM VPI/VCI values. ONUs 120 transmit respective data to OLT 130 during different time slots allocated by OLT 130 for each ONU 120. Splitter 140 splits a single line into multiple lines, for example, 1 to 32, or, in case of a longer distance from OLT 130 to ONUs 120, 1 to 16.
In the related art, PONs are classified into one of the following: an ATM PON (APON), a broadband PON (BPON), an Ethernet PON (EPON or GE-PON), and a Gigabit PON (GPON). The APON uses the ATM protocol; the BPON is designed to provide broadband services over an ATM protocol; the EPON accommodates an Ethernet protocol; and the GPON is utilized when accommodating both the ATM protocol and the Ethernet protocol. Each type of PON is a standardized technology as detailed in Table 1.
TABLE 1PON TypeStandardBPONITU-T G.983.xITU-T G.983.3EPONIEEE 802.3ahGPONITU-T G.984.2
OLT 130 and ONUs 120 provide the interface between the optical network and homes or businesses, and thus define the type of the PON. For example, in order to establish a BPON the OLT 130 and ONUs 120 should be compatible with the BPON standards, i.e., ITU-T-G.983.X series. Specifically, an ONU includes a PON processor utilized to receive downstream traffic from an OLT, and provide the contents of the downstream traffic to one or more subscriber devices. Similarly, the processor of the ONU is deigned to receive and transmit upstream data from the one or more subscriber devices to the OLT via the passive optical network. An example of such PON processor may be found in U.S. patent application Ser. No. 10/340,635 entitled “Integrated PON processor” which is incorporated herein by reference for its useful background description of the state of the art heretofore.
A limitation of PON processors known in the art is the inability to operate in multiple PON modes. For example, the PON processor described in US Patent Application Publication No. 2004/0136712 is compliant only with the ITU G.983.X recommendations. This requires from service providers additional investments in infrastructure when upgrading their PONs, for example, from EPON to GPON.
Therefore, in the view of the limitations introduced in the prior art it would be advantageous to provide an enhanced PON processor adapted to operate in a mixed-mode. It would be further advantageous if the PON processor were compatible with the GPON standard.